The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Some vehicles include a powerplant and an automatic transmission that transmits drive torque at various gear ratios or ranges to a drivetrain. Typically, the transmission includes a torque converter for coupling the transmission and the powerplant. A geartrain transmits drive torque transmitted by the torque converter at the various gear ratios or ranges. The transmission may further include hydraulic elements (e.g., valves, actuators, and the like) that control operation of the torque converter and the geartrain. The transmission may further include a fluid pump for generating pressurized fluid within the transmission used to operate the hydraulic elements.
For example, the torque converter may include a hydraulically-actuated lock-up clutch operable to selectively mechanically couple a pump element and a turbine element. The geartrain may include one or more hydraulically-actuated mechanisms, such as a friction clutch, that selectively couple various components of the geartrain and thereby vary the gear ratio at which the drive torque is transmitted.
Transmission control systems have been developed to control the fluid pressures at which a transmission is operated. However, the control systems may operate the transmission at fluid pressures above those required to properly operate a particular transmission. The fluid pressures are typically higher than required to account for variation in transmission builds and variation during use.